Electric control system



March 7, 1933. Q wHlTNEY 1,900,596

ELECTRIC CONTROL SYSTEM Filed Sept. 4, 1930 Inventor; Chaney Fi whitney,

His Attorney.

Patented Mar. 7, 1933 UNITED STATES PATENT. OFFICE CHANG! I. WHITNEY, OF SOOTIA, NEW YORK, ASSIGNOR 130 GENERAL ELECTRIC COMPANY, .ACOBPOBA'IION OF NEW YORK I morale coma/or. srsrmr Application filed September 4, 1580. Serial No. 479,758.

1 My invention relates to electric control systems and more particularly to manually operable electric control systems in which the supply of current from an alternating our- 5 rent source to a load circuit is controlled in response to the position'of the body of an operator.

Heretofore numerous arrangements have been devised for controlling electric window displays. These arrangements usually include some form of master control switch for either operating the window display devices continuously or in a redetermined sequence. It is an object o my invention to provide an improved arrangement for controllingan electric window display in which the operation of the display is initiated in response to the position of an observer. However, it is to be clearly understood that my invention has many other applications and maybe used in any case where it is desired to control an electric circuit in response to the change of position of a body with respect to some portion of that circuit.

In accordance with my invention I connect an electric window display or its control circuit to a source of alternating current through a vapor electric discharge device or any other desired form of electric valve. The control grid of the electric discharge device is com nected to a point of the supply source of intermediate potential so as normally to keep the discharge device non-co ducting. There is also a connection from the grid to a sheet of metal or metal foil on the window or within the reach of an observer. When the observer approaches this metal sheet or places his hand or some portion of his body in proximity thereto, the capacity of his body changes the impedance of the grid circuit in such a way as to impress a more positive potential upon the grid and thus render the electric discharge device conducting to initiate operation of the window display.

A better understanding of my invention together with other and further objects thereof may be had from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

I have shown in the drawin a source of alternating current 10 connecte to a load 11 through a transformer 12 and a vapor electricdischarge device 16. "It is to be understood that the load. device 11 maybe either the circuit of the electric window display itself or the master switch of its control circuit, in case there are a number of devices to be operated in a predetermined sequence. The vaporelectric discharge device 16 includes a cathode 13, an anode 14 and a control grid 15 which, as is well understood by those skilled in the art, controls the starting of the current through the device but has no further control over the current once it has been initiated in the device. However, when used in an alternating current circuit as illustrated, the anode voltage and current both pass through zero once each cycle,'so that the grid regains control once each cycle. The load circuit 11 is connected in series with the anode and cathode of the discharge device 16, and a portion 17 of the secondary winding of the transformer 12. Across the terminals of the secondary winding of the transformer are 7 connected condensers 19 and 20 which may be either fixed or variable. In some instances it has been found desirable to shunt the condenser 19 with a high resistance 24. The control grid 15 is connected to the intermediate connection between these condensers. There is also a connection from the control grid 15 to a metal plate 22. The terminal of portion 17 of the secondary winding of the transformer is connected to ground at 21.

The operation of the system will be clearly understood from the following explanation: The value of the condensers 19 and 20 is so chosen that normally a slight negative potential is impressed upon the grid 15 so as to 99 render the discharge device 16 non-conducting. When an observer approaches the metal plate 22 or some portion of his body comes in proximitythcreto the capacity of his body completes a parallel circuit around the condenser 20 as illusirated by the equivalent circuit at 23. This results in a decrease in impedance between the grid and ground with the result that the potential of the grid is increased with respect to its cathode and the 100 discharge device 16 is made conducting to operate the window display. It is, of course,

vious that, when the observer passes on,

the control grid will again become negative and the display device will be deenergized at the beginning of the next half-cycle.

While I have shown and described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim

in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a system for controlling an electric circuit in response to the change of position of a body with respect to some portion of said circuit, the combination of a source of current, a load device, a vapor electric valve provided with a control grid, interconnecting said source and said load, an impedance bridge connected across said source, an intermediate point of said bridge being connected to said grid to render said discharge device normally non-conducting, said impedance bridge including a capacitance the magnitude of which is dependent upon the position of said body, by means of which said valve is rendered substantially fully conductive by relatively small changes in said capacitance.

2. In a manually operable electric control system the combination of a source of alter- .4. In a manually operable electric control with an anode, a cathode, and a control grid,

a capacity bridge connected across said source, one side of said bridge being grounded, a connection from said grid to a point in said bridge negative with respect to said cathode normally to render said discharge device non-conducting, and a second circuit between said grid and ground adapted to include the body capacity of the operator, by

means of which said discharge device may be made substantially fully conductive.

In witness whereof, I have hereunto set w my hand this 3rd day of September, 1930.

CHANCY F. WHITNEY.

nating current, a load device, a vapor electric discharge device provided with a control grid, interconnecting said ''source and said load, an impedance bridge connected across said source, an intermediate point of said bridge being connected to said grid to render said discharge device normally non-conducting and a second circuit connected to said grid including a capacitance the magnitude of which is dependent upon the position of the operator, by means of which the discharge device may be rendered substantially fully conductive.

3. In a manually operable electric control system, the combination of a source of alternating current, a load device, a vapor electric discharge device provided with an anode, a cathode and a control grid, interconnecting said source and said load, a capacity bridge connected across said source, a connec ion from said grid to a point in said bridge negative with respect to said cathode normally to render said discharge device 50 non-conducting, and means for changing the balance of the bridge to render said discharge device substantially f ully conductive, comprising a second circuit in shunt to a portion of said bridge, whose capacitance is dependent upon the position of the operator. 

